<html>
  <head>
  base head

  extension head
</head><body>
    <span wicket:id="panel"><wicket:panel>
  <span wicket:id="panelLabel1">label 1</span>
  <wicket:child><wicket:extend>
  <span wicket:id="extendLabel">extension label</span>
</wicket:extend></wicket:child>
  <span wicket:id="panelLabel2">label 2</span>
</wicket:panel></span>    
  </body>
</html>